A proposal to guarantee metrological traceability in determination of heavy metals contents in cork stoppers by ICP-MS

The compliance of heavy metals contents in cork with European Legislation for materials in contact with food and beverages are an important requirement of safety and quality of cork stoppers. However there are few specific regulations for cork. Therefore metrological strategies to assure reliability of analytical measurement results are crucial to ensure that the quantification of chemical contaminants are effectively in line with limits established in law. In this work a general approach is described for implementation of metrological traceability covering all analytical procedure for determination of Arsenic, Lead, Nickel, Chromium and Cadmium contents in cork stoppers with the potential to migrate to beverages. A flowchart diagram to identify the critical points of experimental procedure that need to be under metrological conditions is described. The experimental procedure encompasses the test conditions to simulate migrations for beverages, digestion procedure and determination by ICP-MS. The most important metrological control points to assure that measurements will be traceable to SI were: validation of analytical method to assure correct identification and quantification of metal under study; measurement of recovery of the spikes to estimate analyte lost during the digestion of samples; use of appropriate calibrants to calibrate the ICP-MS; regular participations in PT schemes for contaminants under study; estimation of associated measurement uncertainties. This metrological approach seems realistic to guarantee the traceability of assigned values of inorganic contaminants in cork stoppers and to demonstrate concordance of test conditions with ISO/IEC 17025 requirements.

These work was completed on behalf of Project Liracork, nº 5012 funded by QREN – Sistemas de Incentivos à Investigação e Desenvolvimento Tecnológico (SI-I&DT), Portuguese Government